The present invention relates to an outlet wind velocity measuring apparatus for a filter that is used in a clean bench.
Conventionally, it has been desirable for measurement of the wind velocity in a work space of the clean bench to carry out at the wind outlet side of filter.
However, if the filter has a complicated structure such as, for instance, a high capability one in which each filter element is offset to form a corrugated shape from air intake side to air outlet side, thereby providing a greater filtering area, there has been a problem that such a corrugated structure can cause the outlet wind velocity to vary at the air outlet side in the direction along the filter (that is, in the direction transversely crossing the air flow) and thus it is not possible to measure the wind velocity correctly.
Therefore, it has been suggested for measuring the wind velocity of the filter having the complicated structure as mentioned above to employ a method of detecting a volume of wind at the filter inlet side and of converting this value into the wind velocity, or in the case of measuring the wind velocity at the air outlet side, its measurement has been made at a position relatively remote from the filter's underside. The former method has a problem that greater fluctuations in the measurement values impair results of measurement, while the latter method is also problematic in that necessity of installing a measuring apparatus within the working space inevitably sacrifices the space available for the working operation.